1. Field of the Invention
The invention relates to the preparation of aminomethylene compounds by aminomethylenation of C-H-acid compounds in a single-step reaction.
Aminomethylene compounds, such as aminomethylenated dinitriles, cyanoacetic esters and malonic esters, are important C.sub.3 and C.sub.4 units in the synthesis of heterocyclic compounds, such as for example derivatives of pyrazole, pyridine and quinoline, which are used as active ingredients for pharmaceuticals and as crop protection agents (U.S. Pat. No. 4,620,865).
2. Description of the Related Art
A number of processes for the aminomethylenation of C-H-acid compounds are known and are listed in German Offenlegungsschrift 39 25 720. This German Offenlegungsschrift itself describes the reaction of C-H-acid compounds with alkoxymethylene-iminium salts or with formamidinium salts, alcoholates being used as the bases required. However, alcoholates are expensive and require elaborate handling because of their reactivity. Furthermore, there is the danger that transesterification reactions may occur when esters are used as the C-H-acid compounds. In DD 257 067, the aminomethylenation of cyanoacetate using the DMF (dimethylformamide)-dimethyl sulphate adduct in the presence of sodium carbonate is described, although yields of only 53-61% of the theoretical yield were achieved.